Melt spinning



Sept. 19, 1961 R. c. HART MELT SPINNING Filed Jan. 26, 1959 I0 FEEDHOPPER 23 PUMP 28 SPINNERETTE 30 co/vmm/ER 6 19 SPINNUPETTE RobertC.Hart

United States Patent 3,000,053 MELT SPINNING Robert C. Hart, Kingsport,Tenn., assignor to Eastman Kodak Company, Rochester, N.Y., a corporationof New Jersey Filed Jan. 26, 1959, Ser. No. 789,049 4-Claims. (Cl. 18-8)This invention relates to melt spinning of textile filaments and moreparticularly to an improved melt spinning system especially adapted forspinning textile filaments from polyesters.

Polyesters in the melted phase undergo a decrease in intrinsic viscositywith respect to time. To spin filaments of uniform quality it isdesirable that all of the material extruded through the spinnerettes beheld in the melted phase for a uniform time of short duration.

The usual melt spinning system consists of a melter in which polyesterpellets are melted and pumped into a pipe which delivers the liquidpolyester to a number of metering pumps from which the polyester ispumped to a spinnerette. There is one metering pump for each spinningposition. The metering pump delivers a precise quantity of moltenpolyester at the necessary pressure to force the polyester through theassociated spinnerette.

When one or more of the spinnerettes or other components of a spinningposition fails to function properly, the associated metering pump mustbe stopped with the result that the holdup time in the entire systemback to the meter is increased. This additional holdup time causes adecrease in the polyester intrinsic viscosity and other undesirablechanges in properties of the filaments being spun from the remainingoperable spinnerettes.

It is an object of the present invention to provide an apparatus andmethod whereby uniform intrinsic viscosity and related properties of thefilaments being melt spun from the operable positions are maintainedeven though one or more of the positions, normally operating, betemporarily inoperable. Other objects will appear hereinafter.

In accordance with the present invention, these and other objects areattained by maintaining a constant molten polyester holdup timeindependent of the number of spin positions being operated.

A feature of this invention is the provision of an additional meteringpump down stream of the melter and upstream of the metering pumpssupplying the spinnerettes and adapted to discharge a portion of themolten polyester out of the system, as to a container. This pump willnormally be operated at a very low rate with a flow just sufiicient toprevent the pump from becoming obstructed with solidified polyester.

In the event one or more spinning positions become inoperable and themelt holdup time tends to increase, this additional metering pump,henceforth termed the utility pump, is operated at a faster rate to keepthe flow rate through the melter constant and maintain the constantholdup time essential for close control of filament properties.

My invention will be further understood by reference to the accompanyingdrawing in which melt spinning apparatus is shown in combinationcomprising a feed hopper 10, a melt extruder 11, a motor 12 adapted todrive the extruder, pipes 13 to 18 for conducting molten polyester torespective spinnerettes 19 to 22 and pumps 23 to 26 to force thepolyester through the respective spinnerettes to form filaments.

Pipe 27 branches from pipe 13 and conducts molten polyester tospinnerette 28 where it is forced therethrough by utility pump 29 toform filaments which are retained in container 30. The pipes 13 to 18and 27 are preferably heated to maintain the polyester in a meltedcondition.

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The operation of my invention is now further described. During normalmelt spinning operations, metering pumps 23, 24, 25 and 26 deliverconstant metered quantities of molten polyester to their respectivespinnerettes. The holdup time of the molten material from the melter tothe metering pump and spinnerettes is constant and substantially thesame for the four spinning positions.

The utility pump 29, however, is allowed to run at a much slower rate,the rate being just sufficient so that pump 29 and spinnerette 28 willnot become obstructed by solidified material.

Now assuming that spinnerette 19 malfunctions and pump 23 must bestopped, it is apparent that the system holdup time from the melter tothe spinnerettes is thus increased by 25%.

In such an event, the utility pump 29 is speeded up to reduce the holduptime of the material going to spinnerettes 20, 21 and 22 to exactly thenormal time as though all four, instead of three, productionspinnerettes were operating.

When the malfunctioning of spinnerette 19 has been restored to workingcondition, the utility pump 29 is slowed to its normal slow speed, andpump 23 is started. Normal spinning is thus resumed from all fourspinnerettes.

The utility pump need not necessarily be a metering pump but could beany kind and any number of metering devices for permitting a knownquantity of molten polyester to be extracted from the system for purposeof controlling the holdup time of the molten material.

The utility pump also has other desirable functions. It can serve as ameans for obtaining samples of the melted polyester for laboratoryanalysis or the like.

The utility pump may also be employed to control time dependentproperties of the polyester. For example, molten holdup time within thesystem can be decreased to permit spinning of polyester of initial lowintrinsic viscosity. By running the utility pump at the necessary speedand permitting that portion of the polyester passing through the utilitypump to go to waste, the remaining material reaching the spinnerettescan be spun with less holdup time in the molten condition than normaland consequently a fiber of normal quality may be obtained from materialhaving an intrinsic viscosity somewhat lower than that normallyrequired. A viscosity sensing device installed in the molten polyesterstream in conjunction with a controller varying the utility pump speedcould control viscosity at the spinning positions by varying the systemholdup time.

The utility pump may also be employed to rid the system of moltenmaterial which may be unsuitable for passing through the spinnerettes.

I claim:

1. Apparatus for melt spinning synthetic filaments from a melt spinningcomposition, comprising in combination, a supply source of melt spinningcomposition, a plurality of filament-forming spinnerettes, conduit meansfor conducting the melt spinning composition from the supply source tosaid spinnerettes, means associated with each spinnerette for forcingthe composition therethrough at substantially a constant rate to formfilaments, an additional outlet means connected to said conduit meansdownstream from the supply source and upstream from the filament-formingspinnerettes, means associated with said outlet means adapted duringnormal spinning operation to force melt spinning compositiontherethrough and out of the system at a rate substantially less thansaid constant rate, but adapted tooperate at least at said constant ratewhen any malfunction develops during spinning whereby the holdup time ofthe spinning composition in the apparatus is maintained constant.

2. Apparatus for melt spinning synthetic filaments from a melt spinningcomposition, comprising in combination, a supply source of melt spinningcomposition, a plurality of'filament forming spinnerettes, conduit meansfor conducting the melt spinning composition from the supply source tosaid spinnerettes, pump means associated with each spinnerette forforcing the composition therethrough at substantially a constant rate toform filamerits, an auxiliary spinnerette connected to said conduit 3.Apparatus for melt spinning synthetic filaments from a melt spinningcomposition, comprising in combination, means for melting thecomposition, a plurality of filament-forming spinnerettes, conduit meansfor conducting the melted composition from said melting means to saidspinnerettes, means for forcing said melted composition through saidconduits, pump means associated with each spinnerette for forcing thecomposition there- 'through at substantially a constant rate to formfilaments,

an auxilliary spinnerette connected to said conduit means downstreamfrom the melting means and upstream from the'filament-formingspinnerettes and having pump means associated therewith adapted duringnormal spinning operation to pump said composition therethrough and ,4out of the system at a rate substantially less than said constant ratebut adapted to ,operate at least at said constant rate when any of saidother spinnerettes malfunction whereby the holdup time of the spinningcomposition in the apparatus is maintained constant.

4. Apparatus for melt spinning synthetic filaments from a melt spinningcomposition, comprising in combination, a melt extruder, a plurality offilament-forming spinnerettes, a conduit system for connecting the meltextruder with the spinnerettes, a pump associated with each spinneretteadapted to force the spinning composition therethrough at substantiallya constant rate to form filaments, an auxilliary spinneretteconnected'to said conduit system downstream from the melt extruder andupstream from the filament-forming spinnerettes and having a pumpassociated therewith adapted during normal spinning operation to pumpsaid composition therethrough and out of' the system at a ratesubstantially less than said constant rate but adapted to operate atleast at said constant rate when any of said other spinnerettesmalfunction whereby the holdup time of the spinning composition in theapparatus is maintained constant.

References Cited in the file of this patent UNITED STATES PATENTS2,087,016 Bradshaw et a1. July 13, 1937 2,877,495 Wegener et a1. Mar.17, 1959 FOREIGN PATENTS 687,739 Great Britain Feb. 18, 1953 760,329Great Britain "Oct. 31, 1956

